I've been syncing hours of video with recorded "wild sound" for the past 10 years using the "track stretch" feature in the Vegas Pro editor. All you have to do with Vegas is sync the start of your long audio track, then jump to the end of your audio track and "stretch" the audio to match with the video track, then export everything with a high quality "editing" CODEC. ( I use the Cineform CODEC to export )
If it's a multi-cam shoot, then I base everything on one video track as the "master" track, then stretch both the audio and the other video tracks to sync with the "master" track, and then export all of the different video tracks with a high quality "editing" CODEC. It's pretty easy to do, though you may find some of your cameras are out of sync by as much as half a frame, which is fine as long as you stick with one audio track for everything.
Vignetting is possible depending on which SpeedBooster adapter you use. The Metabones 0.64x adapter has some vignetting problems with certain lenses. The 0.71x adapter seems to have fewer vignetting issues.
The other thing to keep in mind is that Micro 4/3 PRO grade lenses are sharper than adapted APS-C or Full Frame lenses, and can be controlled by the camera. For example the new DJI Ronin-S gimbal has a follow-focus wheel on the left side of the gimbal to allow you to focus with the GH5 / GH5s cameras when using native Panasonic lenses. ( right now this is a GH5 / GH5s ONLY feature for the Ronin-S gimbal )
Other ND issues to be aware of...
- Color casts from both fixed single density and variable ND filters
- Infrared color contamination from cameras that are sensitive to infrared light
( this turns black colors into rusty-browns ), and this can become a big problem when using stronger ND filters. The premium ND filters will block IR color contamination.
After using at least five different brands of variable ND filters over the past 10 years, I have now switched to the B+W XS-Pro Digital ND Vario MRC-Nano filters, which provide you with 1 to 5 F-stops of variable ND. These filters appear pretty neutral color wise, but I have not tested them for IR contamination because most of my Panasonic cameras don't show IR problems, but I have access to one Sony ENG camera that I know has IR issues, so I'm going to test this in the next few weeks.
Can you bring it into Adobe Media Encoder and see that all tracks are recognized ?
What about After Effects ?
If large CFAST 2.0 cards come down in price, then the Canon C200 looks like a winner. I just wish it had non-RAW 10-bit internal recording. ( RAW-lite is a very card hungry format )